[5] pry(main)> User.where(email: 'mpokress@gmail.com').explain
  User Load (25.9ms)  SELECT "users".* FROM "users" WHERE "users"."email" = $1  [["email", "mpokress@gmail.com"]]
=> EXPLAIN for: SELECT "users".* FROM "users" WHERE "users"."email" = $1 [["email", "mpokress@gmail.com"]]
                                     QUERY PLAN
-------------------------------------------------------------------------------------
 Index Scan using index_users_on_email on users  (cost=0.42..8.44 rows=1 width=2198)
   Index Cond: (email = 'mpokress@gmail.com'::text)
(2 rows)

[6] pry(main)> User.where(email: 'mpokress@gmail.com').select(:email).explain
  User Load (31.1ms)  SELECT "users"."email" FROM "users" WHERE "users"."email" = $1  [["email", "mpokress@gmail.com"]]
=> EXPLAIN for: SELECT "users"."email" FROM "users" WHERE "users"."email" = $1 [["email", "mpokress@gmail.com"]]
                                       QUERY PLAN
----------------------------------------------------------------------------------------
 Index Only Scan using index_users_on_email on users  (cost=0.42..8.44 rows=1 width=23)
   Index Cond: (email = 'mpokress@gmail.com'::text)
(2 rows)